1. Field of the Invention
The present invention relates to a method for manufacturing a curved rubber pipe and a device therefore.
2. Description of the Background Art
In order to manufacture a curved rubber pipe, for example, a pipe bent three-dimensionally, conventional operations included a fitting step for covering a straight pipe-like molding material (hereinafter referred to as a rubber semi-finished product) of an unvulcanized or semivulcanized rubber on a curved mandrel, a vulcanizing step for forming a rubber pipe fixed in a curved shape by heating and vulcanizing the rubber semi-finished product in a condition fitted on the mandrel, and an extracting step for removing the vulcanized rubber pipe from the mandrel.
Also, in the fitting step, die lubricant has been applied to facilitate connecting and disconnecting of the rubber semi-finished product to the mandrel. This step of applying has been done by manually dipping the rubber semi-finished product into a tank containing the die lubricant.
During the fitting step, the rubber semi-finished product which is easily bent is fitted to the mandrel by being manually pushed in a direction of the mandrel. The fitting must be carefully effected by the slow and relatively time consuming step of pushing so that the rubber semi-finished product does not buckle or bend during the fitting. Besides being time consuming, this step is difficult to automate.
Also, the extracting step is effected by the manual operation because it is difficult to automate it. The rubber pipe immediately after vulcanizing is handled at a condition of high temperature in order to lessen an extracting load when the curved rubber pipe is removed from the mandrel. For this reason, the operation is forced to be performed in a very difficult operating environment with high temperature and high humidity. Thus, it is necessary for the operator to take relatively frequent rest periods and also, it is difficult to raise the operating efficiency.
On the one hand, in the aforesaid step applying the die lubricant, it is impossible to avoid the die lubricant being applied on inner and outer surfaces of the semi-finished rubber product. However, the die lubricant is required to be applied only on the inner surface of the rubber semi-finished product. It is unnecessary and uneconomical for the die lubricant to be applied to the outer surface.
It is also necessary to effect a dripping out treatment in which the excess die lubricant is dripped out from the rubber semi-finished product pulled up from the tank after dipping, and excess time is required for this treatment.
Further, the dripping treatment has a tendency to worsen the operating environment depending on conditions in which the tank for die lubricant remains opened and the die lubricant is spilled on floor surface. Costs are incurred to effect a draining treatment together with cleaning.
Then, it is an object of the present invention to provide a method and a device for manufacturing a curved rubber pipe which is capable of improving the operating efficiency of the fitting step, adapting to bulk production, and attaining automation.